NAIROBI, Kenya — Opposition supporters boycotted Thursday's rerun of Kenya's disputed presidential election, clashing with police in some parts of the East African country and forcing authorities to postpone voting in areas affected by the violence. At least four people were killed.

While most of Kenya was peaceful, voter turnout was relatively low even in some regions considered to be strongholds for President Uhuru Kenyatta, who was declared the winner of an Aug. 8 election that later was nullified by the Supreme Court in a decision seen as precedent-setting for Africa.

Polling stations in some areas supporting opposition leader Raila Odinga didn't open at all because of sporadic unrest in which police fired bullets and tear gas at stone-throwing protesters who heeded his call for a boycott and maintained the election was not credible.

Voting in four counties, including the opposition stronghold of Kisumu, will be held Saturday, said Wafula Chebukati, chairman of Kenya's electoral commission.

A police statement late Thursday said one person died of a gunshot wound in Kisumu County when about 300 people "stormed into" a vote counting center. It said another person was shot dead in Homa Bay in western Kenya when hundreds of people tried to force their way into a police base.

A third person died at a Kisumu County hospital after being brought in by someone who said he had been shot in a confrontation, the statement said.

Earlier Thursday, a police source said another person was killed in Athi River town outside the capital, Nairobi. The police source spoke on condition of anonymity because they were not authorized to speak to reporters.

Police reported violence in five of Kenya's 47 counties.

Protesters set fires and blocked roads in Kisumu, where 25 people were injured in clashes with police, said Aloyce Kidiwa, a county medical officer. The injuries included many gunshot wounds, Kidiwa said.

Not a single ballot box was delivered to central Kisumu's 190 polling stations, said a senior election official, John Ngutai Muyekho. He sat with the uncollected boxes in a school guarded by security forces.

"If anyone comes to collect, I'm ready. But so far no one has," Muyekho said.

One Kisumu school that saw huge lines of voters on Aug. 8 was closed, its gates locked.

"We are not going to vote and we are not going to allow it," said Olga Onyanga, an Odinga supporter.

Violence also erupted in Nairobi's Kibera and Mathare slums. In Mathare, an Associated Press photographer saw protesters stopping people to check their fingers for the telltale ink stains that proved they voted. In one case, they harassed a woman until police scattered them with tear gas.

The Supreme Court nullified the August election because it found what it called illegalities and irregularities — the first time a court in Africa had overturned a presidential vote. The ruling was sharply criticized by Kenyatta, who seeks a second term. He voted again in his hometown of Gatundu, saying he will work to unify the country if re-elected.

"What we have is a problem of tribalism, and tribalism is an issue that we must continue to deal with and fight with as we continue to develop our country," Kenyatta said.

Many observers say Kenya's ethnic-based politics overshadow the promise of its democracy. Kenyatta, who got 54 percent of the vote in August, is from the Kikuyu group; Odinga, who got nearly 45 percent in the earlier election, is a Luo.

Odinga has said the new election wouldn't be credible due to a lack of electoral reform. He accused Kenyatta of moving a country known for relative stability and openness toward authoritarian rule.

Odinga and Kenyatta also faced off in a 2013 election similarly marred by opposition allegations of vote-rigging. The opposition leader also ran unsuccessfully in 2007, and ethnic-fueled animosity after that vote killed more than 1,000 people and forced 600,000 from their homes.